This invention relates to analog sampled data processing devices, and more particularly to charge transfer devices for performing programmable convolution operations and discrete Fourier transform operations on sampled analog signals. A programmable convolution operation is a convolution with an impulse response which is adjustable. Charge transfer devices include both charge coupled devices (CCDs) and bucket brigade device (BBDs).
The field of use for sampled data processing devices is very broad. Typical uses include processing of signals in radar systems, sonar systems, and communication systems.
In the past, sampled data processing devices were essentially confined to digital signal processors. Analog signals were converted to digital signals by an analog-to-digital converter, and a digital processor operated on the converter's output signals.
More recently, analog devices have been implemented which perform signal processing operations directly on analog signals. For example, U.S. Pat. No. 3,942,035 issued to Dennis Buss on Mar. 2, 1976 describes an invention which utilizes charge coupled devices (CCDs) to perform a chirp Z transform directly on sampled analog signals. As another example, co-pending application Ser. No. 554,884 by C. Hartmann, filed Mar. 3, 1975 describes an invention which utilizes surface wave devices to perform convolution operations directly on continuous analog signals.
Charge transfer signal processing devices offer significant advantages over digital signal processors. They have a smaller size and lesser weight. They also consume less power, and are less expensive.
However, the art of charge transfer signal processing is relatively new and undeveloped. For example, it is believed that no charge transfer device exists for performing a programmable convolution operation on an arbitrary input signal. In addition, no disclosure has been found which teaches the use of a read-only-memory, or a read/write memory, or a discrete Fourier transform unit to generate the adjustable impulse response of the programmable convolver.
Co-pending application by C. Hartmann describes an invention for performing convolution operations on analog signals, but many important differences exist between the invention herein described and the invention described in the co-pending application. For example, the latter utilizes surface wave devices; and their physical structure, principle of operation, and frequency range of operation are entirely different from charge transfer devices. In addition, the surface wave device operates on complex signals as a whole, rather than on real and imaginary components separately. And it also performs continuous transform and inverse transform operations, as opposed to discrete transform and inverse transform operations. These are substantial differences, for they grossly affect the structure of the invention, the speed of operation, and the result obtained.
U.S. Pat. No. 3,942,035 issued to Dennis Buss describes a charge transfer device for performing discrete Fourier transform operations. But it describes no apparatus for performing programmable convolution operations. In addition, the Buss patent does not describe any device for performing discrete Fourier transforms on input signals having both real and imaginary components. Nor does it suggest the use of charge transfer devices having dual impulse responses to reduce hardware.
Therefore, it is one object of the invention to provide a programmable convolver comprised of charge transfer devices.
It is another object of the invention to provide a programmable convolver having an impulse response which is stored in digital memory.
Another object of the invention is to provide a convolver having an impulse response which is generated by taking the discrete Fourier transform of the desired impulse response.
Another object of the invention is to provide a convolver comprised of charge transfer devices having dual impulse responses.
It is another object of the invention to provide a discrete Fourier transform unit that is capable of operating on complex input signals.
It is another object of the invention to provide a discrete Fourier transform unit comprised of dual impulse response charge transfer devices.